You want your plants to look attractive.
Adding rocks or pebbles on top of the potting soil seems to do this.
But is there any harm in doing this?
You can put rocks on top of potted plants as mulch to regulate temperature, prevent weeds, avoid soil erosion, and splashing soil on the foliage. The rocks can be used to give an aesthetic look to the plants.
In general, adding rocks to the top of your potted plants will not harm them; however, there are some exceptions to this rule.
Here you will learn when to top potted plants with rocks, what types of rocks to use, and more.
Let’s get started.
What are the benefits of putting rocks on top of potted plants?
1. Improve aesthetics of the potted plant
The first reason home gardeners choose to put rocks on top of their potted plants is the aesthetic looks. Some prefer the look of rocks instead of the bare soil.
If your main goal is to improve the look of the plant, choose a rock color that compliments the color of the plant. In general, white, gray, or light orange rocks look good in potted plants.
White rocks especially create a more sophisticated look, taking your potted plant from a common house plant to a decorative piece.
2. Helps with water retention in the potting soil
The first way that rocks help your potted plant thrive is with water retention. When you pot your new plants, you likely looked through different soil types and found a “well-draining” mix.
Well-draining soil ensures that the water does not evaporate before the plant can absorb it. You can increase the water retention of your potted plant by placing rocks on top of the soil. The rocks shade the soil from sunlight, reduce its temperature, and help with slow evaporation.
You can consider the rocks as gravel mulch for houseplants or potted plants as they perform the same function as mulch.
I asked 100 gardeners if they use rocks on their potted plants. 76.2% did not prefer to use those. Only 23.8% thought it was a good idea. Here are the results.
3. Protects potting soil from erosion
Putting pebbles on top of potted plants can reduce soil erosion. How often have you watered your plant and watched its precious soil splash out of the container?
If this happens at all, it has happened too many times. The water will run over the rocks after placing rocks on top of your potted plants’ soil, preventing soil loss.
If your potted plants are outside, top dressing with rocks can also protect the plants from wind erosion. This will keep your plants healthier and reduce your trips to the garden store for more soil.
4. Keeps pets away from the potting soil
We love our potted plants, and we love our pets. Unfortunately, they rarely love each other. Pets, especially cats, can damage potted plants.
Cats see larger potted plants as convenient litter boxes. You can try every home remedy in the book to stop this behavior, but some cats are not bothered by cayenne pepper on the soil.
Young fungus gnats will chew and consume the roots of plants. When enough fungus gnat offspring live in the soil, they can completely eat up the root system of a plant.
Fungus gnats as adults live above the soil. They prefer to lay their eggs in the topmost layer of the soil- generally the top 1/4″. A rock layer can help create a barrier for adults looking to lay their eggs.
Topdressing your potted plants with rocks will stop your cat from using the pot as a bathroom.
Playing in the plants can also be harmful to your pets. Eating the soil or other substances in the pot could make your pet sick. Prevent this from happening with a top dressing of rocks.
What are the problems of putting rocks on top of potted plants?
As mentioned earlier, not every plant benefits from a rock top dressing.
Some gardeners agree that the climate the plant lives in affects whether rocks should be placed on top of its plant or not. Plants growing in warmer temperatures and exposed to direct sunlight should not have rocks on top of the soil.
While the rocks will shade the soil from the drying sunlight, they could retain the heat themselves. If they get too warm, it could “cook” the plant’s roots. It is best to only top dress potted plants with rocks when they are not directly exposed sunlight.
You should also be cautious when adding rocks to slow-draining soil. The rocks might impair the potting soil’s limited ability to absorb water. Always pair a top dressing of rocks with well-draining soil.
How to put rocks on top of potted plants
There is more to top dressing a potted plant with rocks than just grabbing a handful of gravel and tossing it in the plant’s container.
First and foremost, make sure you are using a pot that has drainage holes in the bottom. This will prevent water build up in the bottom of the pot that could later lead to rot. If your pot does not have drainage holes already, you could drill a few on your own.
Watch the following video to learn how to drill drainage holes in different types of pots.
In addition to using a specific type of pot, you should use certain kinds of rocks for potted plants. If you use any random rock, it could affect the pH of the soil and potentially kill the plant. For example, limestone raises the pH levels of the soil.
Acceptable rock types are glazed rocks (primarily for aesthetic appeal, brick chips, river rocks, and crushed gravel. You could also use sand as a top dressing material. Sand will prevent bugs from laying their eggs in the soil while still allowing moisture to reach the plant’s roots.
Before topdressing your potted plants, research their preferred soil acidity. After adding the top dressing, take the soil’s pH level frequently to ensure it does not harm the plant.
Lay a thin layer of the selected rocks on top of the soil. Be careful not to overfill the pot with rocks. The soil should still have some access to oxygen. Additionally, too many rocks could compress the soil. Compressed soil does not drain well and decreases its oxygen levels.
Want to increase the water retention of your potted plants without placing the rocks on top of the soil? Put the rocks at the bottom of the pot instead. Once again, be careful with the type and amount of rocks used. Too many rocks could clog the pot’s drainage system.